Obtaining cork acids



Feb. 3, 1959 R. 2. BROWN ET AL 2,87

OBTAINING CORK ACIDS Filed May l, 1956 lo 0 SEPARATION or ACIDS BY SELECTIVE ACID PRECIPITATION FROLI 1somum 51: us

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OBTAINING CQRK ACIDS Ruth Z. Brown and Benjamin Rosen, Baltimore, Md, assignors to Crown Cork & deal Company, inn, Baltimore, Md., a corporation of New York Application May 1, 1956, Serial No. 531,924

13' Claims. (Cl. 260-419) This invention relates to the separation of phloionic and phloionolic acids from cork and the obtaining of pure phloionic and pure phloionolic acids.

Phloionic acid is also known as 9,10-dihydroxy hexadecane dicarboxylic acid and phloionolic acid is otherwise known as tri-hydroxy stearic acid.

In the past it has been found extremely difficult to separate these two acids from each other, and it has also been found extremely difficult to remove these two acids from cork in relatively pure form.

Previously, a mixture of phloionic and phloionolic acids has been obtained by the saponification of cork using strong alkalis, such as caustic soda and caustic potash. This method of obtaining the acids has proven unsatisfactory in that excessive treatment is required to purify the acids and, in addition, the reaction liquor is Q very strongly alkaline and it is diificult to separate the liquor from the insoluble solids. Furthermore, in addition to the phloionic and phloionolic acids, other materials which are soluble in strong alkalis go into solution and further compound the difficulties.

Accordingly, it is an object of the present invention to obtain pure phloionic acid and pure phloionolic acid in a simpler and more economical manner than has been feasible in the past.

A further object is to separate a mixture of phloionic and phloionolic acids from cork in a novel manner wherein the purification steps are reduced.

Yet another object is to obtain a mixture of the calcium salts of these acids.

A still further object is to obtain such calcium salts free from the insolubles normally present in cork.

A still further object is to separately precipitate phloionic acid and phloionolic acid from a solution of the alkaline salts of these materials.

Still another object is to separately dissolve phloionic and phloionolic acid from a solid mixture of these two materials.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

In brief, in the preferred method of operation according to the present invention, cork is treated with a weakly alkaline calcium oxide slurry to obtain the soluble calcium salts of phloionic and phloionolic acids, the insolubles are separated and then the free acids are precipitated as a mixture and then the precipitated mixture of free acids is treated in one of two fashions. In the first procedure, the mixture of precipitated free acids is dissolved in an alkali metal hydroxide solution and then by careful adjustment of the pH the two acids are separately precipitated. In the event that there is some mixing of Fatented Feb. 3, 1959 the two acids in the early stages of the precipitation, the solid mixture can be separated into its components by extraction with alkali metal acetate.

The second method of purification involves taking the precipitated mixture of acids from the calcium hydroxide treatment of cork and extracting with an alkali metal acetate to recover phloionic acid from the early extractions and phloionolic acid from the later extractions.

While the preferred procedure as outlined above involves both the calcium oxide or other alkaline earth metal oxide or hydroxide treatment followed by the sub sequent solution of the mixed acids with separation thereafter, it is possible to obtain some of the benefits of the present invention merely by employing the novel alkaline earth metal oxide or hydroxide treatment and omitting the balance of the procedure. This is particularly true where a mixture of phloionic and phloionolic acids is satisfactory for the subsequent intended use.

Similarly, the second stage of the treatment, i. e., solution with alkali metal hydroxide, and then careful adjustment of the pH or alternatively solution with alkali metal acetate, can be employed with the conventional separation from cork rather than the novel alkaline earth metal oxide separation.

in the drawings:

Figure 1 is a graph for the separation of phloionic acid and phloionolic acid by precipitation from the sodium salts wherein the abscissa is the amount of acid added and the ordinate is the pH;

Figure 2 is a graph similar to Figure 1 for precipitation from the potassium salt; and

Figure 3 is a flow sheet showing the separation of pure acids from the crude mixture of phloionic and phloionolic acid by the use of potassium acetate.

in accordance with the present invention cork is saponitied with a Weakly alkaline calcium oxide slurry. This slurry will have the pH of a saturated solution of calcium oxide. ln place of calcium oxide there can be employed calcium hydroxide or other alkaline earth metal oxides and hydroxides, e. g., magnesium oxide, magnesium hydroxide, barium oxide and barium hydroxide. Preferably, however, calcium oxide or hydroxide is employed. When the cork is saponified with the weakly alkaline calcium oxide solution, phloionic and phloionolic acids dissolve in the form of their soluble calcium salts. As the reaction liquor is much less alkaline than the sodium hydroxide liquors employed in the past, separation of the reaction liquor from the insolubles has been found to occur in a much easier fashion, while at the same time, the reaction liquor does not contain materials which are difiicult to separate from the phloionic and phloionolic acids.

The reaction can be carried out in aqueous medium at a temperature from room temperature to reflux temperature, or if pressure equipment is employed temperatures above the normal reflux temperature can be used. in general, the higher the reaction temperature the shorter the reaction time, and by using superatmospheric pressure with corresponding increases in temperature, the time of reaction can be further shortened.

It has been found that by using an excess of lime there is no need to control the pH in any other fashion, as an excess of lime insures the proper pH.

A typical example of saponification of cork with lime to obtain a mixture of phloionic and phloionolic acids is as follows:

EXAMPLE I Saponificationof cork with lime 1500 ml. water 30 gms CaO 20 gms. ground cork The above mixture was heated at reflux for 20 hours. At the end of this time, the liquor was separated from the solids by filtration to give liquor A. To the insoluble residuewas added a fresh portion .of 1,000 ml. water and this mixture was refluxed overnight. After this treatment, the second saponification liquor Was separated from the solids by filtration to give liquor B. Liquors A and B were separately acidified to Congo Red with concentrated HCl and the precipitate obtained separated by filtration from the residual liquors. The yield of mixed acids containing phloionic and phloion olic was 1.97 gms. (M. P. 112-117 uncorr.) from liquor A and 0.25 gms. (M. P. 100-106 uncorr.) from liquor B.

A mixture of phloionic and phloionolic acids can be separated into its components by dissolving the solid mixture in an alkali metal hydroxide solution and then by careful adjustment of the pH, the two acids can be separately precipitated. The solid mixture of phloionic and phloionolic acids employed as the starting material can be obtained in any known manner, but is preferably obtained in the manner just described, namely, by precipitation from a solution of the calcium salts of the two acids. The preferred alkali metal hydroxides employed for dissolving the mixed acids are sodium hydroxide and potassium hydroxide. For convenience the dissolution reaction and subsequent precipitation are carried out at room temperature, although higher or lower temperatures can be employed. Acidification is preferably accomplished by the use of dilute (about 0.5 N) hydrochloric acid, although any other acid can be employed which can produce a pH below 5.5, and preferably 5 or below. Illustrative of suchacids are sulfuric acid and acetic acid.

It has been found that at a pH above 5.5, e. g., between 5.6 and 6.6, that phloionolic acid is precipitated to the substantial exclusion of phloionic acid. At a pH between 5.6 and 5.4 a mixture of phloionolic and phloionic acids Will precipitate. All of the phloionolic acid will be precipitated by the time a pH of 5.4 is reached, and thereafter, e. g., at a pH of between 5.3 and 3.5, only phloionic acid will be precipitated. Thus, it is possible to obtain an initial pure phloionolic acid precipitate, a final phloionic acid precipitate and an intermediate precipitate fraction still containing a mixture of these two acids. By careful pH control, especially when using potassium hydroxide, it is possible to eliminate this intermediate fraction. When the intermediate fraction is obtained, it can be separated into its components by repeated extractions with alkali metal acetate, e. g., potassium acetate. The phloionolic acid fraction can be recrystallized from aqueous methanol as can the phloionic acid fraction.

When an intermediate fraction containing a solid mixture of phloionolic acid and phloionic acid is obtained, it can be redissolved in aqueous alkaline solution and then further fractionally precipitated, or else it can be separated into the two separate acids by repeated extractions with weakly alkaline salt solution, such as potassium acetate solution, for example. Also, for further purification, the solid acids can be recrytallized from aqueous alcohols, e. g., aqueous methanol.

EXAMPLE II Separation of phloionic and phloionolic acids by selective acid precipitation from sodium salts 0.9 gm. crude mixed phloionolic and phloionic acids prepared by precipitation from a solution of their calcium salts as set forth in Example I was dissolved in NaOHsolution and adjusted with HCl and NaOH solutions so as to have a slight excess of alkali. This solution was placed in an apparatus arranged for mechanical agitation and pH readings (Coleman meter). Measured increments of 0.5198 N HCl were added with continuous agitation and pH readings were taken after each addition; the results were as shown below:

Ml. acid added: pH 0.00 11.05 0.90 10.73 2.30 6.55 2.70 6.22 3.10 6.02 i 3.48 5.90 3.80 5.80 4.58 5.74 5.30 5.80 6.20 5.68 7.10 5.65 8.33 5.58 9.36 5.32 9.83 5.20 10.60 3.94 11.11 3.53 11.48 3.45 12.00 3.13 12.40 3.04 12.80 3.00 13.30 2.90 14.30 2.75 16.40 2.64 18.45 2.50

These results were plotted on rectangular graph paper as shown in Figure 1. The indicated ranges, based on changes of slope, were chosen. as desirable points of separation.

The total mass was re-dissolved with NaOH solution and the required amount of 0.5198 N HCl was added for range #1. The precipitate was filtered out and to the filtrate was added the required acid for range #2. This second precipitate was filtered out and again the filtrate was acidified for range #3. No further precipitate formed on acidification of the final filtrate.

Each of the three precipitates was individually re-dissolved with NaOH solution, precipitated with HCl (made acid to Congo Red) and washed with water. When dried under vacuum, the following weights and melting points were determined:

Fraction 2 was recrystallized from 3% aqueous potassium acetate solution followed by 70% aqueous methanol in the following manner:

The material was heated with 50 cc. 3% potassium acetate and then cooled to room temperature. The liq uid was separated from the insoluble portion by filtration. The filtrate was acidified to Congo Red with cone. HCl and the precipitate A filtered 01f. The original insoluble portion was treated with 50 cc. 3% potassium acetate in a similar fashion and upon acid treatment gave a precipitate B. A third extraction with cc. potassium acetate solution followed by acid treatment gave precipitate C. Precipitates A and B separately recrystallized from 10 cc. of 70% aqueous methanol gave phloionic acid; C recrystallized from 40 cc. 20% aqueous methanol gave phloionolic acid.

The separated product yielded 180 mg. of phloionolic acid (M. P. corr. 100.5-102" C.) and mg. phloionic acid (M. P. corr. 124126 C.).

Fraction 3 was recrystallized from 70% aqueous methanol to yield 260 mg. phloionic acid (M. P. corr. 122.5-123.5 C.)

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EXAMPLE n1 Separation of phloionic and phloionolic acids by selective acid precipitation from potassium salts The technique was similar to that described for formation of the sodium salts in Example II except that potassium hydroxide was used in place of sodium hydroxide. The relation of pH to ml. acid added is shown on the graph set forth in Figure 2, along with the ranges chosen for separation. In this case four samples of precipitate were recovered which after recrystallization from 70% aqueous methanol yielded phloionolic acid from fractions #1 and #2 and phloionic acid from #3 and #4.

The method of separation illustrated in Examples 11 and III results in purer materials with fewer steps and larger percentage yields than are possible with prior art methods of separating phloionolic acid from phloionic acid.

Another novel method of separating phloionolic acid from phloionic acid forms a different phase of the present invention. In this method there can be used a solid mixture of phloionic and phloionolic acids derived from any source but preferably by co-precipitation of their calcium salts with acid. The mixture of solid acids is then repeatedly extracted with an aqueous solution of an alkaline salt having a pH in aqueous solution substantially the same as that of potassium acetate. The alkaline salt employed in the extraction should be able to increase the pH from about 3.5 to about 6.6 as the extractions progress. Phloionic acid is obtained from the earlier extractions and phloionolic acid from the later extractions, the general method of carrying out the separation being illustrated in the flow sheet, Figure 3.

In place of potassium acetate there can be used sodium acetate and similar alkali metal salts of materially weak acids. in place of hydrochloric acid as the precipitating agent there can be employed sulfuric acid or even acetic acid. The separated precipitates from each extraction are then preferably recrystallized from aqueous methanol to insure the purity of the products obtained. This method of separation of phloionolic acid from phloionic acid results in obtaining purer acids with fewer operating steps than is possible with the previously known methods of separating mixtures of these two acids.

EXAMPLE IV Separation of phloionic and phloionolic acids by treatment with potassium acetate The raw material used was a mixture containing phloionic and phloionolic acids prepared by precipitation from a solution of their calcium salts as set forth in Example I. 2.83 gms. of this material was mixed with successive 100 ml. portions of 3% aqueous potassium acetate. At each step, the mixture was heated to boiling and then cooled to room temperature, the insoluble portion removed by filtration and again treated with 100 ml. of the 3% aqueous potassium acetate solution; the filtrate in each instance after removal of the insoluble portion was acidified to Congo Red with concentrated HCl to precipitate the desired organic acids. This scheme is shown in Figure 3. In the figure, the steps above the arrowed lines take place before the steps immediately under the line.

Six samples of precipitate were collected from the hydrochloric acid treatments in addition to a small amount of insoluble residue. These had the following melting points (uncorr.):

5B 103-108 #6 95-102 Insoluble residue -97 #5 was further separated with 2 successive 50 ml. portions of 3% aqueous potassium acetate solution followed by precipitation with concentrated hydrochloric acid into 5A and 5B, as shown.

Samples #2, 3, 4 and 5A were combined and recrystallized from 56% aqueous methanol to yield 890 mg. of phloionic acid, M. P. corr. l23.5124.5 C. Samples #SB and 6 were combined and recrystallized from 20% aqueous methanol to yield mg. of phloionolic acid, M. P. corr.-10l-102 C.

This separation is believed to involve a pH phenomenon since it is, in effect, similar to the selective precipitation from alkali metal hydroxide solution by acid technique, although operating from the opposite direction.

This procedure is also operative with other alkaline compounds that form soluble salts with phloionic and phloionolic acids. Thus, water soluble calcium salts of weak acids and potassium and sodium salts of weak acids other than acetic acid can be used.

Phloionic acid can be used to prepare civetone, a perfume ingredient, and both phloionic and phloionolic acids can be used as individual ingredients for preparing waxes, resins, plasticizers, lubricants and detergents. Thus, either phloionic acid or phloionolic acid can be esterified with methyl alcohol. Similarly, the sodium salt of phloionolic acid can be used as a detergent as can the potassium salt of phloionic acid.

We claim:

1. A process of separating phloionic acid from phloionolic acid comprising extracting a solid mixture of these two materials with an aqueous solution of an alkaline salt having a pH in aqueous solution of 6.6, said extraction being repeated a plurality of times and recovering phloionic acid from the earlier extracts by acidification and phloionolic acid from the later extracts by acidification.

2. A process according to claim 1 wherein the salt is an alkali metal salt.

3. A process of obtaining pure phloionic acid from a mixture of phloionic acid and phloionolic acid comprising extracting a solid mixture of these acids with aqueous potassium acetate at a pH up to 5.4 and then recovering pure phloionic acid from the aqueous extract by acidification.

4. A process of separating phloionic acid from phloionolic acid comprising extracting a solid mixture of these acids initially at a pH below 5.4 in a plurality of aqueous extraction stages at increasing pH values with each successive extraction up to a pH of 6.6 and adding acid to the earlier extracts to precipitate pure phloionic acid therefrom.

5. A process of separating a mixture of solid phloionic and phloionolic acids comprising mixing the said mixture with 3% aqueous potassium acetate, heating said mixture containing aqueous potassium acetate to boiling,

cooling to room temperature, removing the insoluble portion by filtration, acidifying the aqueous liquor to obtain a precipitate, treating the insoluble portion from the first aqueous potassium acetate extraction with a further amount of 3% aqueous potassium acetate and continuing the process to obtain a plurality of aqueous potassium acetate extracts and a plurality of acid precipitates therefrom whereby substantially pure phloionic acid is recovered from the earlier potassium acetate extracts and phloionolic acid is recovered from the later potassium acetate extracts.

6. A process of separating a mixture of solid phloionic acid and phloionolic acid comprising dissolving the mixture of acids in aqueous alkali metal hydroxide and acidifying the solution to a pH of above 5.6 to precipitate in a first stage phloionolic acid and thereafter further acidifying the molten liquor at a pH below 5.6 to precipitate in a second stage phloionic acid.

7. A process of separating a mixture of solid phloionic acid and phloionolic acid comprising dissolving the mixture of acids in an initial aqueous alkali metal hydroxide and then acidifying the solution to a pH between 5.6 and 5.4 to precipitate substantially all of the phloionolic acid and only a part of the phloionic acid, re-dissolving the precipitate in aqueous alkaline solution and then further fractionally precipitating the phloionolic acid at a pH between 5.6 and 6.6 and further acidifying the initial alkali metal hydroxide solution to a pH below 5.4 to precipitate substantially pure phloionic acid.

8. A process of separating a mixture of phloionic and phloionolic acids comprising dissolving the mixture in an aqueous alkali metal hydroxide solution, acidifying the mixture to a point not lower than about 5.3 to obtain a precipitate of phloionolic acid and a filtrate containing the alkali metal salt of phloionic acid.

9. A process of obtaining pure phloionic acid comprising dissolving a mixture of phloionic acid and phloionolic acid in an aqueous alkali metal hydroxide solution, acidifying the mixture to a point not lower than about 5.5 to obtain a precipitate of phloionolic acid with some of the phloionic acid and then further acidifying the filtrate to a pH below 5.4 to recover a precipitate of substantially pure phloionic acid.

10. A process according to claim 8 wherein the alkali metal hydroxide is sodium hydroxide.

11. A process according to claim 8 wherein the alkali metal hydroxide is potassium hydroxide.

12. A process of obtaining pure phloionic and phloionolic acids comprising treating cork with aqueous alkaline earth oxideto form the alkaline earth metal salts of said acids, separating the alkaline liquor from the insoluble residue, acidifying the alkaline liquor to a pH below 5.6 to precipitate a mixture of phloionic and phloionolic acids, treating the mixture of said acids With aqueous alkali metal hydroxide to dissolve the same, acidifying the alkali metal hydroxide solution to a pH of about 5.4 to 5.6 to precipitate in a first stage a mixture of phloionolic acid and phloionic acid and thereafter further acidifying the mother liquid at a pH below 5.4 to precipitate substantially pure phloionic acid in a second stage.

13. A process according to claim 12 including the further step of extracting the phloionolic acid and phloionic acid first stage mixture a plurality of times with an alkali metal acetate and recovering pure phloionic acid from the earlier extracts by acidification and pure phloionolic acid from the later extracts by acidification.

References Cited in the file of this patent UNITED STATES PATENTS Dupont et al. Oct. 16, 1951 

1. A PROCESS OF SEPARATING PHLOIONIC ACID FROM PHLOIONOLIC ACID COMPRISING EXTRACTING A SOLID MIXTURE OF THESE TWO MATERIALS WITH AN AQUEOUS SOLUTION OF AN ALKALINE SALT HAVING A PH IN AQUEOUS SOLUTION OF 6.6. SAID EXTRACTION BEING REPEATED A PLURALITY OF TIMES AND RECOVERING PHLOIONIC ACID FROM THE EARLIER EXTRACTS BY ACIDIFICATION AND PHLOIONOLIC ACID FROM THE LATER EXTRACTS BY ACIDIFICATION. 